Many modern technological applications require high quality crystals for use in, for example, semiconductor and optical devices. Accordingly, many crystal growth techniques have been developed and brought to a high degree of perfection.
One technique of particular interest for growth of semiconductor devices such as, for example, lasers and photodetectors, is liquid phase epitaxy (LPE). In this technique, a boat, typically comprising carbon, holding a semiconductor wafer is placed under a melt containing semiconductor material. Prior to contact with the wafer or substrate, the solution is saturated or slightly undersaturated and has an initial temperature, T. The temperature of the melt is now decreased after contact with the substrate and epitaxial growth begins. After the desired amount of epitaxial growth has occurred, the wafer with the epitaxial layer is removed from contact with the solution by sliding the boat. Further layers may be grown with varying thicknesses, compositions, etc.
Most LPE growth techniques are directed toward obtaining uniform growth, i.e., obtaining growth on all areas contacted by the melt. However, selective area liquid phase epitaxy techniques are known and useful. One prior art selective area growth technique using LPE involved the use of a dielectric film deposited on a GaAs surface of a dielectric insert to serve as a mask. In this technique, no epitaxial layer will grow over the masked surface while an epitaxial layer grows over the unmasked surface. For a more detailed description of this technique, see, for example, U.S. Pat. No. 3,978,426 issued on Aug. 31, 1976 to R. A. Logan et al.